The Future of the Haringvliet Sluices

Abstract

The
Haringvliet sluices is one of the Delta Works. The sluices were finished in
1970 and are thus 50 years old. This research is initiated because the expected
lifetime of hydraulic structures is thought to decrease significantly due to
climate change. This study aims to provide insight in the functions the
Haringvliet sluices fulfill and to what extent climate change influences the
functioning of the Haringvliet sluices. If the lifetime of the current
structure is reached multiple other strategies are suggested. The lifetime of
the sluices is determined, based on the effect of climate change on the
functions the sluices fulfils. The climate scenarios used for the assessment of
the sluices are the KNMI’14 climate scenarios (Gl and Wh). These are the most mild
and most extreme scenarios. The amount of sea level rise and the change in
annual river discharge distribution of these scenarios are used for the
assessment of the sluices.   For the
assessment of the Haringvliet sluices, multiple tools are used. Calculations
are made with the programs SOBEK and Hydra-BS, available literature is used,
information received from interviews with experts and hand calculations have
been used as tools to assess the Haringvliet sluices.  Flood protection, fresh water availability
and ecology are the functions for which the sluices have been assessed. Another
failure mechanism for which the sluices have been assessed is structural
failure. The lifetime for which the sluices fail constructively are conducted
by a semi-structured interview. Not opening, not closing, overtopping and
overflow are the failure mechanisms included in the assessment for flood
protection. The effect of the failure mechanisms in combination with climate
change may not lead to hydraulic loads which exceed the retaining height with
0.2 meter of at least two dike sections at the hinterland. With the
Kierbesluit, the Haringvliet sluices are opened during high-tide. The
requirement concerning fresh water availability is that the chloride
concentration at Middelharnis-Spui may not exceed 300 mg/litre. The requirement
for ecology is based on fish migration in combination with the Kierbesluit.
Multiple fish species must be able to migrate from the North-Sea to the
Haringvliet for at least 50\% of the time as indicated for each specie in the
migration calender. The sluices may also not be closed for 50 consecutive days.
This reduces migration via the Haringvliet. 
The lifetime for which the function of flood protection is reached, is
based on literature, spreadsheet calculations and the use of the models
SOBEK-RE and Hydra-BS. With SOBEK-RE water level calculations are carried out
in which the failure mechanisms of not opening and not closing are added. The
results have been stored in a database which is used as input for Hydra-BS.
Hydra-BS probabilistically calculates water levels through the south western
delta. The effect of the failure mechanism of overtopping is calculated by
calculating overtopping volumes with formulas found in prior research (Van der
Meer, 2008). The overtopping volumes can be significant but due to the large
storage area at the Haringvliet, the effect is relatively small. Also, the
coincidence between a storm at the North Sea and large discharges at the Rhine
is relatively low.  The assessments of
the functions fresh water availability and fish migration are based on the
aggregation of multiple researches in combination with the effect of a changing
climate, for which the KNMI’14 climate scenarios are used. Concluded is that
the function for fish migration cannot be fulfilled in the most extreme
scenario around 2050.  First strategy
proposed to extend the lifetime is to change the Kierbesluit. Sluices may be
opened by lower discharges during high tide. However, this decreases the
lifetime for fresh water availability. The lifetime with another Kierbesluit
can be enlarged by circa 30 years. With this measure the functions of fresh
water availability and fish migration still reach the lifetime first around the
year 2080. Life time extending measures can be thought of and can be of both
economic and social points of view. Closing the sluices more frequently (social
point) reduces the fish migration. Relocating the fresh water intake locations
more upstream or by building a fish passage from the North-Sea to the
Haringvliet is a measure which is coming from an economical viewing point.   When taking into account the extending
measure concerning ecology, the lifetime of the sluices become as follows. In
case of an extreme scenario the functional lifetime can be met until at least
2050 and the structural lifetime is reached around 2100. In case of an average
climate scenario, all the functions fail in a relatively short time span of 20
years, around the year 2130. With the Gl climate scenario used in this thesis
the sluices fail first structurally, which is around the year 2170.   In case of an average or mild climate
scenario, the sluices need to be removed or covered because they fail
structurally. To replace or cover the current Haringvliet sluices when the
lifetime is reached, multiple functional strategies have been developed.  For the development of the new functional
strategies it is assumed that the requirements do not change compared to the
current requirements. The functional strategies are based on three possible
designs for the Haringvliet: a permanent closure of the Haringvliet in which
pumps are installed, a similar sluice complex or creating an open estuary
again. These three strategies are used in combination with other structures.
Eventually two verified designs are evaluated. It turned out that closing of
the Haringvliet can fulfil all the requirements. A larger sluice complex
including a fish passage turned out to be the best functional design. With the
rough assumptions used in the evaluation, the variant in which larger sluices
combined with a fish passage is suggested comes out as the best strategy. Other
strategies could turn out to be more suitable for the requirements, criteria
and boundary conditions valid at that moment. Therefore adaptive coastal and
river management is recommended.  What
must be noted is that backward salt intrusion, intrusion via the Nieuwe
Waterweg and Spui to the Haringvliet can cause problems concerning the quality
(salt concentration) of drinking water. Closing the Nieuwe Waterweg is a
solution concerning the requirements composed for the Haringvliet. However, the
effect on the Port of Rotterdam and the costs involved for this closure are not
estimated and are therefore not included in the functional designs.  In this thesis multiple methods are used to
calculate the effect of a failure mechanism of the Haringvliet sluices on the
hydraulic load. Suggested is to come up with a model in which the failure
mechanisms not opening, not closing and overtopping are included. Further, with
the data from Rijkswaterstaat on the chloride concentrations in the Haringvliet
a salt intrusion model can be made to improve the Kierbesluit.